PLC based fractional-order PID temperature control in pipeline: design procedure and experimental evaluation

Meccanica - Fractional-order control system design can be used for systems with non-local dynamics involving long-term memory effects. However, implementation of a fractional-order controller in...     

Enzymatic cascade reactions inside polymeric nanocontainers: a means to combat oxidative stress

Oxidative stress, which is primarily due to an imbalance in reactive oxygen species, such as superoxide radicals, peroxynitrite, or hydrogen peroxide, represents a significant initiator in pathological conditions that range from arthritis to cancer. Herein we introduce the concept of enzymatic cascade reactions inside polymeric nanocontainers as an effective means to detect and combat superoxide radicals. By simultaneously encapsulating a set of enzymes that act in tandem inside the cavities of polymeric nanovesicles and by reconstituting channel proteins in their membranes, an efficient catalytic system was formed, as demonstrated by fluorescence correlation spectroscopy and fluorescence cross-correlation spectroscopy. Superoxide dismutase and lactoperoxidase were selected as a model to highlight the combination of enzymes. These were shown to participate in sequential reactions in situ in the nanovesicle cavity, transforming superoxide radicals to molecular oxygen and water and, therefore, mimicking their natural behavior. A channel protein, outer membrane protein F, facilitated the diffusion of lactoperoxidase substrate/products and dramatically increased the penetration of superoxide radicals through the polymer membrane, as established by activity assays. The system remained active after uptake by THP-1 cells, thus behaving as an artificial organelle and exemplifying an effective approach to enzyme therapy.     

Synthetic polyion-counterion transport systems in polymersomes and gels

Transport across the membranes of polymersomes remains difficult in part due to the great thickness of the polymer bilayers. Here, we report that dynamic polyion-counterion transport systems are active in fluorogenic polymersomes composed of poly(dimethylsiloxane)-b-poly(2-methyloxazoline) (PDMS-PMOXA). These results suggest that counterion-activated calf-thymus DNA can act as cation carrier that moves not only across lipid bilayer and bulk chloroform membranes but also across the "plastic" membranes of polymersomes. Compared to egg yolk phosophatidylcholine (EYPC) lipsosomes, activities and activator scope in PDMS-PMOXA polymersomes are clearly reduced. Embedded in agar gel matrices, fluorogenic PDMS-PMOXA polymersomes respond reliably to polyion-counterion transporters, with high contrast, high stability and preserved selectivity. Compared to standard EYPC liposomes, it cannot be said that PDMS-PMOXA polymersomes are better. However, they are different, and this difference could be interesting for the development of sensing devices.     

Squeezed states of a particle in magnetic field

For a charged particle in a homogeneous magnetic field, we construct stationary squeezed states which are eigenfunctions of the Hamiltonian and the non-Hermitian operator , and Ŷ being the coordinates of the Larmor circle center and Φ is a complex parameter. In the family of the squeezed states, the quantum uncertainty in the Larmor circle position is minimal. The wave functions of the squeezed states in the coordinate representation are found and their properties are discussed. Besides, for arbitrary gauge of the vector potential we derive the symmetry operators of translations and rotations. Fiz. Tverd. Tela (St. Petersburg) 40, 1405–1412 (August 1998) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

Protein-polymer nanoreactors for medical applications

Major challenges that confront nanoscience in medicine today include the development of efficacious therapies with minimum side effects, diagnostic methods featuring significantly higher sensitivities and selectivities, and personalized diagnostics and therapeutics for theragnostic approaches. With these goals in mind, combining biological molecules and synthetic carriers/templates, such as polymer supramolecular assemblies, represents a very promising strategy. In this critical review, we present protein-polymer systems as reaction spaces at the nano-scale in which the enzymatic reactions take place inside polymer supramolecular assembly, at its interface with the environment or in a combination of both. The location of the protein(s) with respect to the polymer assembly generates a diversity of systems ranging from nanoreactors to active enzymatic polymer surfaces. We describe these both in terms of general modelling and addressing the specific conditions and requirements related to the medical domain. We will particularly present protein-polymer nanoreactors that provide protected spaces for enzymatic reactions. We also show how polymer supramolecular structures, such as micelles, capsules, dendrimers and vesicles, can accommodate sensitive biomolecules to mimic natural systems and functions, and to serve as avenues for new medical approaches. Even though not yet on the market, we will emphasize possible applications of protein-polymer systems that generate reaction nanospaces-as novel ways to advanced medicine (264 references).